1. Field Of The Invention
The present invention relates to composite connecting members in the form of couplings and fittings for hydraulic fluid lines, and specifically to couplings and fittings having a body made from a first material formed about a second material.
2. Related Art
Fittings for providing a leak-proof attachment between a hydraulic or other fluid conducting tube and associated hardware, such as actuators, manifolds, etc., are well-known. One type of well-known fitting is that shown in the Rosan Sr. patent, U.S. Pat. No. 3,702,707, incorporated herein by reference.
One form of such a hydraulic fitting is shown in FIG. 1, labeled as prior art. The fitting combination 10 includes a fitting 12 threaded into a parent or base material 14 through external threads 16. The parent material may be steel, aluminum or any other material forming the particular housing or hardware to which a fluid connection is to be made. A cavity 18 connects a passage way 20 through which the fluid is passed. The fluid may be hydraulic or pneumatic and under working pressure up to 8,000 psi, for example.
The fitting 12 includes an O-ring groove 22 for maintaining an O-ring 24 against a first counterbore 26 in the parent material. The O-ring groove is located on the outer surface of the fitting between the threads 16 and a conically shaped, upwardly diverging surface 28. The conically shaped surface 28 terminates at a series of longitudinally extending serrations 30, which extend in a direction parallel to a central axis 32 of the fitting combination. The fitting is held in threaded engagement with the base material 14 by a lock ring 34 having internal serrations 36 that mate with the external serrations 30 on the fitting. The lock ring further includes external serrations 38 for engaging the parent material in a second counterbore 40. The lock ring 34 prevents rotation of the fitting relative to the parent material, thereby preventing the fitting from backing out of the parent material when under operating conditions. The longitudinally extending serrations 30 on the fitting, in conjunction with the serrations on the lock ring, are also used for tightening down the fitting into the parent material or removing the fitting, with an appropriate tool (not shown).
The fitting 12, on an upper or second end portion 42, includes external threads 44 for engaging a coupling nut (not shown) for a hydraulic fluid line. The coupling element threadably engages the fitting at the upper portion thereof so that a seal can be formed between the hydraulic tubing and the second end portion 42 of the fitting.
The fitting shown in FIG. 1, when used for high pressure applications, is typically manufactured from a metal, such as aluminum, titanium or steel. Fittings such as are made from the above-mentioned materials form, when taken in aggregate for such applications as with aircraft, etc., a non-neglible part of the total weight of the aircraft.
Couplings for connecting a pair of hydraulic tubes together are also well known.